1. Technical Field
The present invention proposes a simple and rapid method for fabricating metallic self-organized nanodots on the surface of a transparent conductive oxide (TCO), so as to effectively increase the local conductivity of the TCO.
2. Description of Related Art
Indium Tin Oxide (ITO) film is a kind of transparent conductive oxide (TCO) film and plays an important role in Flat Panel displays, such as organic electro-luminescence display (OLED), plasma display panel (PDP), liquid crystal display (LCD), and light emitting diode (LED) display.
Through previous researches and studies, it is able to know that the amorphous ITO film fabricated by sputtering process includes lower surface roughness and higher surface resistance, and performs bad surface current due to the lower surface roughness and higher surface resistance. Accordingly, U.S. Pat. No. 5,163,220 proposes a superstring technique to deposit Ag and Ti films on an ITO film, wherein the Ag and Ti films are taken as metal bus bars for increasing the conductivity of the ITO film, so as to further increase the efficiency of the thin film electroluminescent (TFEL) display using the ITO film as the substrate thereof. Beside the sputtering technique proposed by U.S. Pat. No. 5,163,220, U.S. Pat. No. 7,687,349 forms metallic nanodots on the surface of a dielectric material (i.e., ITO film) by using two processes of: (1) reacting a silicon-containing gas precursor (e.g., silane) to form silicon nuclei over a dielectric film layer; and (2) using a metal precursor to form metallic nanodots where the metallic nanodots use the silicon nuclei from step (1) as nucleation points. Thus, by way of the forming of those metallic nanodots, the surface current of the dielectric film layer is effectively increased.
Differing from the above-mentioned techniques proposed by U.S. Pat. Nos. 5,163,220 and 7,687,349, femtosecond laser surface nanostructuring technique is recently applied in increasing the value added of some materials, such as metal, semiconductor and glass. In the paper published in the international Journal of OPTICS LETTERS, vol. 32, No. 13, p. 1932, 2007, the femtosecond laser pulse is used and focused on a region with few microns size on the surface of a tungsten film, and then linear sub-wavelength periodic nanodots are fabricated and formed on the surface of the tungsten film. In addition, the paper published in APPLIED PHYSICS LETTERS, Vol. 82, No. 25, p. 4462, 2003 proposes how to fabricate the similar sub-wavelength periodic nanodots on the surface of various compound semiconductors by using the femtosecond laser pulse. Moreover, in the paper published in the international Journal of PHYSICAL REVIEW LETTERS, Vol. 91, No. 24, p. 247405-1, 2003, it focuses the single-beam femtosecond laser pulse to the surface of a glass for fabricating some periodic microstructures with the size of 1 μm×1 μm and the spacing of 20 nm. Besides, U.S. Pat. No. 7,438,824 also utilizes and focuses the femtosecond laser pulse to the surface of a transparent or a translucent dielectric material for fabricating periodic microstructures with the assisting of a scanning platform.
Moreover, OPTICS EXPRESS paper of Vol. 18, No. 14, p. 14401, 2010 proposes the optical absorption of two dimensional periodic microstructures on ZnO crystal fabricated by the interference of two femtosecond laser beams. However, the same to the technique of U.S. Pat. No. 7,438,824, the femtosecond laser technique of this OPTICS EXPRESS paper also uses the scanning platform for carrying out the large area fabrication of the periodic microstructures on the surface of ZnO film.
Accordingly, in view of the above-mentioned conventional femtosecond laser techniques, the person skilled in the related art can find that the conventional femtosecond laser techniques include the shortcomings and drawbacks as follows:
1. Those conventional femtosecond laser techniques all utilize high fluences (0.1-0.4 J/cm2) with a focused spot of hundred micrometers on the surface of semiconductor and dielectric materials, owing to the pulse broadening after an objective lens. However, this way still needs the assisting of a scanning platform in order to fabricate large size periodic microstructure on the surface of the dielectric material.2. The periodic microstructures made by using those conventional femtosecond laser techniques are all line patterns rather than nanodots array.
Accordingly, in view of the conventional femtosecond laser techniques still have shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a method for forming superior local conductivity in self-organized nanodots on transparent conductive film induced by femtosecond laser pulses.